Multiple sclerosis (MS) is a chronic, progressive, degenerative disease of the central nervous system (CNS), and particularly of the “white matter” tissue. It is considered an autoimmune disease characterized by inflammation and demyelination of the CNS leading to chronic neuralgic disturbances. Autoantibodies are generated by the immune system against antigens of myelin proteins such as myelin basic protein (MBP) which envelops the spinal cord.
Experimental autoimmune encephalomyelitis (EAE) is the commonly used animal model for MS. It may be induced in wild-type animals such as rodents by inoculation, or appear spontaneously in genetically susceptible strains.
Adenosine receptors are classified into four major classes: A1, A2a, A2b and A3. A3 adenosine receptors belong to the family of the Gi-protein associated cell surface receptors. Receptor activation leads to its internalization and the subsequent inhibition of adenylyl cyclase activity, cAMP formation and protein kinase A (PKA) expression, resulting in the initiation of various signaling pathways(1,2). PKA contains a catalytic subunit PKAc which dissociates from the parent molecule upon activation with cAMP.
U.S. Pat. No. 5,506,214 (Beutler) discloses treatment of patients having MS with therapeutic agents containing substituted adenine derivatives such as 2-chloro-2′-deoxyadenosine (CdA). Treatment with CdA was shown to markedly ameliorate the disease condition. CdA was found to be a putative partial agonist at A1 receptors, as described in Siddiqi, S. M. et al, (1995) J. Med. Chem. 38:1174-1188. The Ki values of CdA for the various adenosine receptors were 7.4 μM at the A1 receptor, 20 μM at the A2a receptor and 207 μM at the A3 receptor.
U.S. Patent Application No. 20020094974 (Castelhano, et al) discloses new N-6 substituted 7-deazapurine derivatives which are A3 adenosine receptor antagonists. These compounds may be used for treating diseases associated with the A3 adenosine receptor, including neurological disorders such as MS.